The criticism
"If what matters is sentience, then the only problem is suffering. Just use anesthesia and everything's solved: we could do anything to animals, as long as it's painless."
Where the mistake is
The criticism assumes that considering sentient beings is only about avoiding suffering. That's false.
Remember: giving someone consideration means avoiding harming them and trying to help them. And there are two ways to harm:
- causing something bad, like pain;
- preventing something good, as happens when someone dies and loses the good things they would still have lived.
Two examples
A painless death. Even if an animal is killed without feeling anything, it loses all the good it would still have had. Anesthesia doesn't fix that.
The prize nobody told you about. Imagine you won a prize, but nobody told you and you never found out. You didn't suffer at all, but you were harmed: you missed out on something good.
To understand these two cases, we have to compare what the person (or the animal) would live through in each situation. That's exactly what the sentience standard does.
In short
- Considering someone means avoiding harming them and trying to help them.
- You can also harm someone by taking away good things, as with a painless death.
- So anesthesia doesn't solve everything.